He was a starter for a successful AC Milan side as a 23-year-old and a key player for Ghana, yet controversy has never been too far away for Boateng.

This is not the first time he will have played in Spain either after spending one season at Las Palmas, following his release from Schalke.

The German-Ghanaian was separated from the squad at Schalke due to disciplinary reasons as he was caught smoking and drinking alcohol prior to a doping test and ultimately he ended up at AC Milan, once again, but he only stayed there for six months before becoming a free agent and joining Quique Setien's side.

At Las Palmas, he recovered his best form - playing alongside the likes of Jonathan Viera and Roque Mesa - and became adored by the club's supporters due to his performances, in addition to his gestures off the pitch.

His controversial moments include picking up an injury in 2012 due to "excessive sex" with Melissa Satta. "He is always injured because we have sex seven to ten times a week," she said.

Boateng has not been afraid to perform bold actions too, such as walking off the pitch after being subjected to racist abuse during a friendly whilst playing for Milan.

Alcohol and junk food

During his time at Tottenham, early in his career, Boateng recognises that his preparation away from the pitch did nothing to aid him on it.

"Every night we went out until six in the morning," he said.

"I weighed about 95 kilograms, I was fat due to alcohol and bad food.

"I couldn't play football, so I bought a Lamborghini; you are happy for a week, after that you never use it again.

"I still have that image: three cars, a big house, standing there like I'm 50 Cent.

"Sometimes I think about it and say, 'Look at how stupid you were,' but that made me who I am now - I learned and grew up."

He went on loan at Borussia Dortmund and, under the tutelage of Jurgen Klopp, he turned things around.

Ballack's executioner

In May 2010, Boateng responded to Michael Ballack in the FA Cup final between Portsmouth and Chelsea, something that earned him the nickname as 'Ballack's executioner'.

Half an hour into the match, Ballack slapped Boateng and two minutes later, he retaliated by kicking him which caused Ballack to pick up an injury.

That injury prevented Ballack from going to the World Cup with Germany and he never returned to his best level; Boateng apologised but many believe that he purposefully injured Ballack.

Thrown out of the World Cup

At the 2014 World Cup, Ghana were preparing to face Portugal in a match that was paramount in ensuring their place in the competition.

A few hours before the game, Ghana coach Kwesi Appiah decided to expel Boateng and his teammate, Sulley Muntari, from the squad.

Appiah claimed that both players had insulted and threatened him, something they denied.

Redemption in the Canary Islands

Having lived a fascinating career to the point he arrived at Las Palmas, Boateng was honest in an interview with MARCA.

"In two years, I spent all my money on cars, clubs, and friends that really weren't," he said.

Boateng made it clear that he did not go to Las Palmas to party, but instead for the footballing project.

Rihanna's tweet about Boateng

Boateng, who Rihanna had a crush on in 2014, went to Eintracht Frankfurt after Las Palmas, followed by Sassuolo, and now he is going to be at Barcelona.

He will be looking to show those in Catalonia that he still has the quality to play at the highest level, rather than demonstrate some of the controversial moments that he has had in the past.